Fiddler is a free and open-source packet analyzer. It is used for network troubleshooting, analysis, software, communications protocol development and education. Fiddler captures HTTP and HTTPS traffic dataÂ between browsers and servers. These data are extremely valuable for troubleshooting, performance turning and system monitoring. This article is a step by step tutorialÂ to guide how to useÂ Fiddler and capture HTTP Traffic.

Capturing of HTTP and/or HTTPS traffic may include private orÂ confidentialÂ information, such as usernames, passwords or bank info. Use caution when entering in sensitive data while Fiddler is configured to capture traffic. If possible, use test or dummy data instead of confidentialÂ data while using Fiddler.

If you are a web developer,Â Fiddler is the must one in your tool kits.

On 12 September 2012 Eric Lawrence announced that Fiddler was acquired by Telerik and he would join the company to work on Fiddler on a full-time basis.

1. FiddlerÂ Overview

Fiddler sits between HTTP client and server and listened on a port. As the finger below, it acts asÂ â€œman-in-the-middleâ€Â proxy, when using fiddler, the requests is being sent directlyÂ to Fiddler proxyÂ bridge, Fiddler will forward the request to real server, Likewise,Â the response from server is also sent to the fiddler, fiddler will forwardÂ it to the browser.Â To the client browser, Fiddler claims to be the web server, and to the web server, Fiddler mimics the web browser. Â In this process,Â Fiddler intercepts andÂ records all the incoming and outgoingÂ messages.

Besides Fiddler, FireBug is an alternative one and most popular and powerful web development tool, it can Inspect HTML and modify style and layout in real-time.

2. DownloadÂ Fiddler

FiddlerÂ is a Windows Forms application,Â available for Windows XP and later, go to download pageÂ http://www.fiddler2.com/fiddler2/, there have two versions fiddler2 andÂ fiddler4Â available,Â fiddler2 wasÂ written in .Net 2,Â fiddler4 was higher, pleaseÂ choose either theÂ one to download.

3. Install Fiddler on yourÂ clientÂ machine

After downloaded, double-click the exe file and agree with the installation license, follow the step-by-step wizard to complete the installation, during installing,Â you may be asked to close all browsers.

4. Start Fiddler

Lunch the shortcut of Fiddler from from Start > All Program, you will see the below main Fiddler UI, when startingÂ Fiddler, it will automatically check the latest version against the FiddlerÂ server and ask you upgrade if there have new version available.

5. UseÂ Fiddler toÂ Capture HTTP or HTTPS traffic

5.1 Check overall Web sessions

Use Internet Explorer or Mozilla FireFox, openÂ a web page that sends a request via the explorer, we will instantly see a list of the web requests in the web sessions panel, while, if you visit more web pages, the recorded requests Â will continue growing and keep in order.

Comments – A text field you can set from scripting or the session’s context menu

The each type of item have an ownÂ icon on the left hand, the below is the list of the all icons.

Of course, It’s just an overall summary list, it give a genericÂ sense that we can choose what we want.

5.2 Â Check FiddlerÂ Inspectors

If you double click on a HTTPÂ session, the Inspectors tab on rightÂ hand will be displayed, itÂ visualize requests or responseÂ content in meaningful ways.Â In the top half of the right hand side is theÂ request what was sent to server, there haveÂ multipleÂ tabs of view where show format message and data(Headers, Text View, web forms, HexView, Auth, Cookies, Raw, JSON and XML). The first one is header, it logged cache, Client, Cookies/Login,Â Miscellaneous and Transport, these infos are particularÂ helpfulÂ to troubleshoot.

Request Inspectors
[RW] Headersâ€”Shows request headers and status.
[RW] TextViewâ€”Shows the request body in a text box.
[RW] HexViewâ€”Shows the request body in a hexadecimal view.
[RO] XMLâ€”Shows the request body as an XML DOM in a tree view.Response Inspectors
[RW] Transformerâ€”Removes GZip, DEFLATE, and CHUNKED encodings for easier debugging.
[RW] Headersâ€”Shows response headers and status.
[RW] TextViewâ€”Shows the response body in a text box.
[RW] HexViewâ€”Shows the response body in a hexadecimal view.
[RO] ImageViewâ€”Shows the response body as an Image. Supports all .NET image formats.
[RO] XMLâ€”Shows the response body as an XML DOM in a tree view.
[RO] Privacyâ€”Explains the P3P statement in the response headers, if present.

The bottom half is the response tab,Â this is the entire response being sent back to the client browser, it may possible be HTML page, image, JSON string, Cascading Style Sheet (CSS) and other resources, we can click textview, syntaxview, Imageview and other clickable tab to view it in different format, the below example demos weÂ syntax view the html source page of this site.

5.3 Â CheckÂ statistics ofÂ the request

Click onÂ statisticsÂ tab, itÂ will show the estimated performance statistics for the selected HTTP sessions. It gives us aÂ straight-forward insight for receive status and chart from high level. It’s good for performance turning.

For instance, the below is theÂ analyticÂ data which retrieved the home page of this site.

fiddler is only debugging tool, which enables the traffic data in your hand. so to fiddler, it is impossible to reduce the server response time, you have to turn your server program then back to fiddler testing again.

You could save some responses in local files and than use the Autoresponser tab to send these files to client. That is faster than downloading content from the server each time, although files will slowly become outdated, and it may be difficult to prepare a lot of them

Hi,
Please let me know how to check the load time of a web page, for instance if I open asjava.com then in statistics tab what is the total load time for the whole page? How to calculate it for the whole page?

I appreciated you came back to check answer, from my point of view, the Fiddler sets up proxy and listens the envelops between the browsers and server. Yahoo massager is an app, it directly talks to Yahoo server and probably Fiddler cannot be in the middle, the alternative solution is to use network Sniffer – Capture TCP/IP packets on your network.

Hello,
Please provide information on data extraction from fiddler, I m using SAZ file from fiddler , but I want to take the exact size of the page and total bytes sent/received from for that page.
Is it possible to extract this total data from SAZ file? Please reply